text: /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   * All rights reserved.
   *
   * This package is an SSL implementation written
   * by Eric Young (eay@cryptsoft.com).
   * The implementation was written so as to conform with Netscapes SSL.
   *
   * This library is free for commercial and non-commercial use as long as
   * the following conditions are aheared to.  The following conditions
   * apply to all code found in this distribution, be it the RC4, RSA,
   * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
   * included with this distribution is covered by the same copyright terms
   * except that the holder is Tim Hudson (tjh@cryptsoft.com).
   *
   * Copyright remains Eric Young's, and as such any Copyright notices in
   * the code are not to be removed.
   * If this package is used in a product, Eric Young should be given attribution
   * as the author of the parts of the library used.
   * This can be in the form of a textual message at program startup or
   * in documentation (online or textual) provided with the package.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *    "This product includes cryptographic software written by
   *     Eric Young (eay@cryptsoft.com)"
   *    The word 'cryptographic' can be left out if the rouines from the library
   *    being used are not cryptographic related :-).
   * 4. If you include any Windows specific code (or a derivative thereof) from
   *    the apps directory (application code) you must include an acknowledgement:
   *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
   *
   * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   * The licence and distribution terms for any publically available version or
   * derivative of this code cannot be changed.  i.e. this code cannot simply be
   * copied and put under another distribution licence
   * [including the GNU Public Licence.] */
  
  #ifndef OPENSSL_HEADER_DH_H
  #define OPENSSL_HEADER_DH_H
  
  #include <openssl/base.h>
  
  #include <openssl/engine.h>
  #include <openssl/ex_data.h>
  #include <openssl/thread.h>
  
  #if defined(__cplusplus)
  extern "C" {
  #endif
  
  
  /* DH contains functions for performing Diffie-Hellman key agreement in
   * multiplicative groups. */
  
  
  /* Allocation and destruction. */
  
  /* DH_new returns a new, empty DH object or NULL on error. */
  OPENSSL_EXPORT DH *DH_new(void);
  
  /* DH_free decrements the reference count of |dh| and frees it if the reference
   * count drops to zero. */
  OPENSSL_EXPORT void DH_free(DH *dh);
  
  /* DH_up_ref increments the reference count of |dh|. */
  OPENSSL_EXPORT int DH_up_ref(DH *dh);
  
  
  /* Standard parameters.
   *
   * These functions return new DH objects with standard parameters. They return
   * NULL on allocation failure. The |engine| parameter is ignored. */
  
  /* These parameters are taken from RFC 5114. */
  
  OPENSSL_EXPORT DH *DH_get_1024_160(const ENGINE *engine);
  OPENSSL_EXPORT DH *DH_get_2048_224(const ENGINE *engine);
  OPENSSL_EXPORT DH *DH_get_2048_256(const ENGINE *engine);
  
  
  /* Parameter generation. */
  
  #define DH_GENERATOR_2 2
  #define DH_GENERATOR_5 5
  
  /* DH_generate_parameters_ex generates a suitable Diffie-Hellman group with a
   * prime that is |prime_bits| long and stores it in |dh|. The generator of the
   * group will be |generator|, which should be |DH_GENERATOR_2| unless there's a
   * good reason to use a different value. The |cb| argument contains a callback
   * function that will be called during the generation. See the documentation in
   * |bn.h| about this. In addition to the callback invocations from |BN|, |cb|
   * will also be called with |event| equal to three when the generation is
   * complete. */
  OPENSSL_EXPORT int DH_generate_parameters_ex(DH *dh, int prime_bits,
                                               int generator, BN_GENCB *cb);
  
  
  /* Diffie-Hellman operations. */
  
  /* DH_generate_key generates a new, random, private key and stores it in
   * |dh|. It returns one on success and zero on error. */
  OPENSSL_EXPORT int DH_generate_key(DH *dh);
  
  /* DH_compute_key calculates the shared key between |dh| and |peers_key| and
   * writes it as a big-endian integer into |out|, which must have |DH_size|
   * bytes of space. It returns the number of bytes written, or a negative number
   * on error. */
  OPENSSL_EXPORT int DH_compute_key(uint8_t *out, const BIGNUM *peers_key,
                                    DH *dh);
  
  
  /* Utility functions. */
  
  /* DH_size returns the number of bytes in the DH group's prime. */
  OPENSSL_EXPORT int DH_size(const DH *dh);
  
  /* DH_num_bits returns the minimum number of bits needed to represent the
   * absolute value of the DH group's prime. */
  OPENSSL_EXPORT unsigned DH_num_bits(const DH *dh);
  
  #define DH_CHECK_P_NOT_PRIME 0x01
  #define DH_CHECK_P_NOT_SAFE_PRIME 0x02
  #define DH_CHECK_UNABLE_TO_CHECK_GENERATOR 0x04
  #define DH_CHECK_NOT_SUITABLE_GENERATOR 0x08
  #define DH_CHECK_Q_NOT_PRIME 0x10
  #define DH_CHECK_INVALID_Q_VALUE 0x20
  #define DH_CHECK_INVALID_J_VALUE 0x40
  
  /* These are compatibility defines. */
  #define DH_NOT_SUITABLE_GENERATOR DH_CHECK_NOT_SUITABLE_GENERATOR
  #define DH_UNABLE_TO_CHECK_GENERATOR DH_CHECK_UNABLE_TO_CHECK_GENERATOR
  
  /* DH_check checks the suitability of |dh| as a Diffie-Hellman group. and sets
   * |DH_CHECK_*| flags in |*out_flags| if it finds any errors. It returns one if
   * |*out_flags| was successfully set and zero on error.
   *
   * Note: these checks may be quite computationally expensive. */
  OPENSSL_EXPORT int DH_check(const DH *dh, int *out_flags);
  
  #define DH_CHECK_PUBKEY_TOO_SMALL 1
  #define DH_CHECK_PUBKEY_TOO_LARGE 2
  
  /* DH_check_pub_key checks the suitability of |pub_key| as a public key for the
   * DH group in |dh| and sets |DH_CHECK_PUBKEY_*| flags in |*out_flags| if it
   * finds any errors. It returns one if |*out_flags| was successfully set and
   * zero on error. */
  OPENSSL_EXPORT int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key,
                                      int *out_flags);
  
  /* DHparams_dup allocates a fresh |DH| and copies the parameters from |dh| into
   * it. It returns the new |DH| or NULL on error. */
  OPENSSL_EXPORT DH *DHparams_dup(const DH *dh);
  
  
  /* ASN.1 functions. */
  
  /* d2i_DHparams parses an ASN.1, DER encoded Diffie-Hellman parameters
   * structure from |len| bytes at |*inp|. If |ret| is not NULL then, on exit, a
   * pointer to the result is in |*ret|. If |*ret| is already non-NULL on entry
   * then the result is written directly into |*ret|, otherwise a fresh |DH| is
   * allocated. However, one should not depend on writing into |*ret| because
   * this behaviour is likely to change in the future.
   *
   * On successful exit, |*inp| is advanced past the DER structure. It
   * returns the result or NULL on error. */
  OPENSSL_EXPORT DH *d2i_DHparams(DH **ret, const unsigned char **inp, long len);
  
  /* i2d_DHparams marshals |in| to an ASN.1, DER structure. If |outp| is not NULL
   * then the result is written to |*outp| and |*outp| is advanced just past the
   * output. It returns the number of bytes in the result, whether written or
   * not, or a negative value on error. */
  OPENSSL_EXPORT int i2d_DHparams(const DH *in, unsigned char **outp);
  
  
  /* ex_data functions.
   *
   * See |ex_data.h| for details. */
  
  OPENSSL_EXPORT int DH_get_ex_new_index(long argl, void *argp,
                                         CRYPTO_EX_unused *unused,
                                         CRYPTO_EX_dup *dup_func,
                                         CRYPTO_EX_free *free_func);
  OPENSSL_EXPORT int DH_set_ex_data(DH *d, int idx, void *arg);
  OPENSSL_EXPORT void *DH_get_ex_data(DH *d, int idx);
  
  
  struct dh_st {
    BIGNUM *p;
    BIGNUM *g;
    BIGNUM *pub_key;  /* g^x mod p */
    BIGNUM *priv_key; /* x */
  
    /* priv_length contains the length, in bits, of the private value. If zero,
     * the private value will be the same length as |p|. */
    unsigned priv_length;
  
    CRYPTO_MUTEX method_mont_p_lock;
    BN_MONT_CTX *method_mont_p;
  
    /* Place holders if we want to do X9.42 DH */
    BIGNUM *q;
    BIGNUM *j;
    unsigned char *seed;
    int seedlen;
    BIGNUM *counter;
  
    int flags;
    CRYPTO_refcount_t references;
    CRYPTO_EX_DATA ex_data;
  };
  
  
  #if defined(__cplusplus)
  }  /* extern C */
  #endif
  
  #define DH_R_BAD_GENERATOR 100
  #define DH_R_INVALID_PUBKEY 101
  #define DH_R_MODULUS_TOO_LARGE 102
  #define DH_R_NO_PRIVATE_VALUE 103
  
  #endif  /* OPENSSL_HEADER_DH_H */
  